Investigation of flow and energy characteristics in aerobic tanks of integrated wastewater treatment equipment using combined particle image velocimetry and computational fluid dynamics methods

Integrated wastewater treatment equipment is widely utilized in remote areas of China due to its compact footprint and low operational costs. However, a lack of detailed understanding of internal flow field characteristics often results in compromised treatment efficiency and excessive energy consumption. This study addresses this gap by employing a hybrid approach integrating particle image velocimetry (PIV) experiments and computational fluid dynamics (CFD) simulations to investigate internal flow characteristics—including velocity fields and vorticity patterns—within the aerobic tank. Through precise regulation of inlet and nitrification reflux velocities, the CFD model was validated against PIV data. The validation scope was expanded from localized subsets to the full computational domain, confirming the predictive accuracy of the CFD model, with a maximum relative error of less than 18.6%. Simulation results demonstrate that at an inlet velocity of 0.697 m/s and a reflux velocity of 0.979 m/s, achieves homogeneous mixing with a stable velocity distribution, uniform vorticity dispersion, and consolidated vortex core structures. This optimized configuration enhances wastewater treatment efficiency while achieving approximately 15% energy savings in pump power.